The present invention relates to a straightening device for elongated round articles, particularly for rods or pipes, of the type which includes a preparatory station for receiving the articles to be straightened, a feeding unit for taking over the articles from the preparatory station and a straightening station arranged subsequent to the feeding station and having driven inclined rollers in alignment with the feeding path of the feeding station.
Due to the preliminary treatment of rods or seamless or welded pipes of steel or non-ferrous metals, for example in drawing machines or rolling mills or in the subsequent feed treatment units, it is normally necessary to straighten such articles before their further processing. For this purpose, straightening machines are known which include inclined rollers rotating at a predetermined rotary speed and calibrated according to a particular range of diameters of the processed pipes.
Due to the calibration of the inclined straightening rollers and in view of a particular diameter of the processed article, the straightening rollers must be adjusted to a certain inclined position at which the articles are processed at desired feeding and rotary speeds. In other words, when the processed articles are of smaller diameter, the straightening rollers must be more inclined in the direction of the center axis of the articles than in the case of larger diameters. Accordingly there is an immediate dependency between the feeding speed and the rotary speed of the processed articles and the angle formed by the longitudinal or center axis of the processed article and the axis of rotation of respective straightening rollers. In addition, at a smaller diameter of the processed article, the rotary speed of the rollers is greater than in the case of larger diameters whereas the feeding speed for articles of smaller diameters must be reduced.
Under these considerations an inference might be drawn that in order to increase output of straightened rods or pipes, only the rotary speed of the straightening rollers must have been increased. Such a measure, however would result in a prohibitive range of rotary speeds of the processed articles. As known, articles of a length of approximately 20 meters tend under the influence of rotary speed and due to their imbalance to jump out of their place and strike against the trough-shaped feeding units. Such strikes become the more stronger the higher is the rotary speed and the more bent is the article. Consequently, the noise levels is excessively increased.
The loading of prior art feeding stations from the prepararory stations takes place along a lateral side of the latter, mostly by separating individual articles from a bundle of articles made ready on the preparatory station. For this purpose, inlet gates have been already developed having relatively narrow clearance. If such inlet gates are opened, their cross-section is sufficiently large for permitting the reception even of strongly bent elongated articles, which upon closing of the gate, still are accommodating in the inlet gate or groove. The reduction of the cross-section of the inlet gate therefore must not reach a point in which the article is clamped and cannot be introduced in the straightening station. In addition, the article in the inlet gate must have sufficient freedom of movement so as to permit straightening rollers to set it in rotation and advance it without problems.
Accordingly, hitherto a compromise had to be made between the desired productive efficiency on the one hand and the rotary speed of the processed article on the other hand in order to avoid damages of the upper surface of the articles caused by the strokes against the inlet gates. In practice, this compromise results in a straightening speed of about 60 meters per minute which can be increased to about 100 meters per minute provided that almost straight articles are fed in and consequently an intake or inlet gate of reduced diameter is needed.
Another critical point of the known straightening devices is the lateral loading of the feeding units with the articles to be processed. As long as the article is present in an inlet gate which is at least partially closed at its top, the subsequent article can be held in a stand-by position above the inlet gate but cannot be introduced in the latter. It can be inserted in the inlet gate only after the discharge of the preceding article. This circumstance, under considering an average straightening speed, necessitates time intervals of about 5 seconds between pipe length of 7 to 8 meters. Such time intervals represent ineffective times in the operation of the straightening device.
In view of the fact that in prior art straightening devices the articles to be processed are introduced laterally from the preparatory station in the feeding station, there is an additional disadvantage in the necessity of manipulation of the articles by the attending personnel. It has turned out that in general a worker can handle articles up to 8 meters long of an average diameter. For articles between 8 meters and 20 meters of length, however, two workers are necessary for shifting the article in the feeding unit. Moreover, since the articles are mostly received on the preparatory unit in jammed bundles, the separation of the articles can be made with an extraordinary effort.
In summary, due to the limited rotary speeds of the processed articles, due to the lateral loading of the articles in the feeding units, due to the requirement of at least two workers for handling longer articles as well due to the necessity of a discontinuous loading of the articles in the device caused by the fact that an article cannot be inserted in the inlet gate before the preceding article is completely discharged the effective operational time of prior art straightening devices amounts only to about 50%.